1 <?php 2  3 class myClass{ 4      5     private static $obj = null; 6  7     private function  __construc(){ 8  9     }10 11     public static function getInterface(){12         if(self::$obj == null){13             self::$obj = new self();14         }15 16         return self::$obj;17     }18 19     public function __toString(){20         return ‘this is __toString‘;21     }22 }23 24 $obj = myClass::getInterface();25 echo $obj;